Just a few years after killings in the Bay Area's biggest cities lurched upward, the state's homicide rate fell to a 44-year low in 2010, officials said, easing concern that a sour economy might translate into desperation and danger on the streets.

Overall violent crime dropped as well, with the number of homicides, robberies, rapes and assaults down 6.4 percent from 2009, according to preliminary figures that the California Department of Justice collected from the state's biggest police agencies and released this week.

Total homicides fell nearly 10 percent in big cities - and 2009 had already been a pretty good year. The state's per-capita homicide rate that year was down 15 percent from 2000.

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Police officials and criminologists said Thursday that they are happy with the trend but don't know exactly what has caused it. Some point to better policing, others to a society in which law-abiding citizens can spread information about crime faster thanks to cell phones and the Internet.

The drop has lessened a noxious element in many Bay Area communities - fear - and has reduced the power of crime as a game-changer in elections. It is certain to play a role in debates over sentencing laws and the size of the state's prison system.

Economic factors

At the same time, the weak economy persists, and there is concern that continued cuts to law enforcement and social services could ultimately snuff out the gains.

"We haven't seen crime this low since Dwight Eisenhower was president. So it is remarkable," said Barry Krisberg, a criminal justice expert at the UC Berkeley School of Law. "You would have bet that, given the economic downturn, you would have seen more crime. But that's kind of a myth. We're challenging a lot of myths."

Although the numbers are encouraging, they also reveal an uneven picture, particularly in the East Bay, where several big cities continue to suffer from high crime rates.

East Bay crime

Oakland had the highest per-capita violent crime rate of any of the 59 California cities with a population of more than 100,000, the figures show. Richmond had the third-highest rate, Antioch the fifth-highest. Berkeley, meanwhile, remained the state's leader in property crime, despite an 8 percent drop last year.

In contrast with the statewide and national trend, violent crime rose in 2010 in Concord, Fairfield and Richmond, and in Santa Clara.

But there is positive news in many big cities. Oakland had 90 homicides last year, compared with 104 in 2009 and 145 in 2006. The number of killings in Richmond fell from 47 to 21 in one year. San Francisco had 48 slayings - slightly up from 2009, but a far cry from the 100 in 2007.

A separate report, released Thursday by the Brookings Institution, found that violent crime fell nearly 30 percent from 1990 to 2008 in the country's 100 largest metropolitan areas. Meanwhile, the gap between violent crime rates in big cities and their suburban neighbors narrowed - the suburbs improved, but less dramatically.

Smarter policing

Richmond Police Chief Chris Magnus, whose city has seen only six homicides this year, said smarter policing played a role in the drop. He cited a revolution in the use of crime data to pinpoint problems, as well as efforts to engage the community.

Gone, he said, are blanket sweeps in rough neighborhoods that "created sort of a siege mentality and alienated people who were already challenged with crime." Instead, police try to focus narrowly on the few people causing the bulk of the problems.

But Magnus cautioned that the new strategies are time-intensive and need resources. Richmond beefed up its police force from 143 to 196 officers in the past six years, while other agencies - like Oakland and Vallejo - cut back because of budget constraints.

Concord Police Chief Guy Swanger, who moved north from the San Diego force in January, said crime fighting has benefited from technological advances, such as better fingerprinting and DNA testing.

Social networking

Residents, too, contribute by sharing and reporting information on cell phones and social networks, he said.

"I think that changes the dynamics," Swanger said. "It's more immediate, and that first 24 hours (after a crime) is really the key to apprehension. Times have changed, and people are a lot more invested and connected in things around them."

Swanger and others concede, though, that these are only theories. As Robert Weisberg, a criminal justice expert at the Stanford Law School, said, "Nobody has any idea why any of this is happening."